Find a decent dealer with a range and they will have a variety of pistols that you can rent so that you can see what works best for you. I'm a glock man myself. Are you looking to conceal it easily ? Try a glock 26, if not try a 17 or 19.
I have a Springfield Armory XDM 9mm. It loads 19+1 in the magazine. Magazines (not the necessarily the weapon) over 10 rounds are illegal in some states (like California). My second 9mm is a baby Glock 26. Both will do the job; however, the Glock would be my choice for concealed carry and the XDM for the range.
Law enforcement has special problems, such as concerns over liability if someone is accidentally shot. For that reason, most departments insist on a sidearm that fires DA only or at least DA for the first shot. I believe most handgun experts would pick a 1911 in .45 cal if given a choice for a handgun to have when they hear something go bump in the night. The extra mag capacity of a 9 mil or .40 is not usually a consideration in the typical home defense scenario. The stopping power of a .45 might be.
I own a .45 and I've fired 9mm's. I'd rather have a .45 than a 9mm in a gun fight. But if I were shopping for a handgun I'd give serious consideration to the .40 cal. Rifles and not handguns but "they" also largely moved away from the 7.62mm to 5.62mm. And now they're breaking out old 7.62 M14's to replace the M16 in certain situations where the smaller caliber just doesn't cut it. The new M110 is also chambered for 7.62. 9mm does have a flatter trajectory but for up close and personal I'd prefer the larger round every time.
some interesting (michigan) fyi: Is it okay to have a pistol with a 15 round clip? Yes, as federal law 18USC Sec 922 effective September 30, 1994 which prohibited an individual from having a firearm with a clip holding over 10 rounds, was repealed effective September 1, 2004. Is it legal to carry a visible pistol in public? Although MCL 750.227 restricts carrying a pistol concealed on your person or in a vehicle, there is no statute that specifically prohibits carrying a visible pistol. MCL 750.234d states that you cannot possess any firearm in a depository financial institution, a church or other house of religious worship, court, theatre, sports arena, day care center, hospital or an establishment licensed under the Michigan liquor control act, unless that possession is with the permission of the owner or his/her agent of the entity. From what I understand about new Michigan laws, it is legal to shoot someone who enters your home uninvited even if they are not armed, and the law further states that no legal recourse can be taken by the family of the person shot, or, by the person shot. If they are where they are not suppose to be, and they know it, you can cap their ass without the worry of legal action... ABOUT F*CKING TIME!!
Never liked the glock. Feels like a cinder block in my hands. As for a kit switching to 9, yes, there is one. But I want a new gun, not a replacement barrel.
No, conceal isn't an issue. Just for fun. In my opinion (i'm sure some here will disagree) but 9mm isn't good for home defense. You get a thug wearing thick winter jackets and it might take a lot of shots to knock him down. with the 40 and hollow points, he's going down quick. So my 226 .40 is fine for defense.
You raise a few points. If you are interested in a handgun to have when you hear something go bump in the night don't overlook the one nobody has mentioned and what I consider the finest single "manstopper", the .357 Magnum. Sure, as a revolver it doesn't have the glitz 'n glamor of a pistol but it provides the finest single-shot defense and, unlike semis, it never jams. Plus, in the middle of the night as you wake up disoriented, there's no concern with whether a round is chambered, whether the safety is on/off, etc. Just pick it up, even if it's been sitting for years, and pull the trigger. The average non-LEO gun battle lasts 2.3 rounds so in the real world those super-extra capacity mags might "feel good" but are meaningless. Bottom line, you're not going to get into a long running firefight where you need a 19-clip 9mm mag. That's comic book fantasy stuff. With a .357 Magnum it's Boom. Hit target. Job done. As an extra all .357 Magnums also fire .38 Special rounds which are much cheaper and great for target practice, tin cans, etc. Also fire .38 Special +P and .38 Special +P+ rounds so you're getting multiple guns in one. Anyway, something to consider.
Magna brings up some good points on a home defense weapon that may sit for years untouched. Magazine springs can lose there "spring" if left compressed (loaded) for extended periods. This can affect feed reliability in semi autos.